1. Field of the Invention
The present invention relates to display systems. More specifically, the present invention relates to systems for improving the image quality of large screen display systems.
While the present invention is described herein with reference to illustrative embodiments for particular applications, it should be understood that the invention is not limited thereto. Those having ordinary skill in the art and access to the teachings provided herein will recognize additional modifications, applications, and embodiments within the scope thereof and additional fields in which the present invention would be of significant utility.
2. Description of the Related Art
Image registration and distortion are critical issues in large screen display design. U.S. Pat. Nos. 4,683,467, issued Jul. 28, 1987 to Macaulay et al., and 5,020,116, issued May 28, 1991 to Macaulay, (the teachings of which are incorporated herein by reference) describe image registration systems which incorporate a photodetector arrangement to align color images in large screen displays. Unfortunately, these systems were not designed to resolve X-Y image distortion, a mispositioning of pixels in the x and y plane of the display.
Barrel distortion and pin cushion distortion are two well known examples of the effects of X-Y image distortion. X-Y image distortion is due to many factors including nonlinearities in deflection circuits and mechanisms and leakages in deflection yokes.
The conventional technique for correcting for distortion in large screen displays is to overlay a grid on the screen and project a test pattern on the screen. A human operator then uses a cursor to move pixels that are out of place to a proper position as determined by the grid. The degree of movement required to position the pixel is stored and used as a correction factor to position pixels of actual image data.
Unfortunately, this process is tedious and error prone. The correction factor may vary with each operator and, in the case of direct view cathode ray tube displays, movement of the operator's head may change the viewing position and introduce parallax error. Also, no reference element is commonly provided so that linearity can not be established accurately.
In the case of projection displays, a carefully ruled calibration reference screen is required. Some mechanism is required to install such a screen on a temporary basis during the convergence and linearity adjustment process. The physical layout of the viewing theater may make even temporary installation difficult or impractical. In addition, there is often no safe vantage point for a human operator.
Thus, there is a need in the art for an automatic system and technique for correcting image distortion in large screen display systems which minimizes the need for operator involvement.